• A. Increased respiratory rate
  • B. Increased vital capacity
  • C. Increased pulmonary perfusion
  • D. Increased tidal volume ✓


Increased minute ventilation during pregnancy is primarily due to an increase in tidal volume. Tidal volume refers to the amount of air that moves in and out of the lungs during normal breathing. During pregnancy, the body undergoes various physiological changes to accommodate the growing fetus, including changes in the respiratory system. The increase in tidal volume allows for more oxygen to be delivered to the fetus and helps meet the increased metabolic demands of both the mother and the developing baby.

In other words, during pregnancy, the maternal metabolic demands increase significantly due to the growth of the fetus and the placenta. This increased metabolic load necessitates an augmented supply of oxygen and carbon dioxide to the mother. To meet this requirement, pregnant women exhibit an increase in minute ventilation (the product of respiratory rate and tidal volume).

Although respiratory rate may also increase during pregnancy, it does not account for the entirety of the increased minute ventilation. The primary contributor is actually an enlargement of the tidal volume, which is the amount of air inhaled and exhaled during a single breath. This expansion occurs due to various physiological adaptations that take place during pregnancy, such as diaphragmatic elevation and relaxation of the smooth muscles lining the bronchioles (1). These changes facilitate a greater intake of air per breath, thereby enhancing gas exchange and ensuring adequate oxygenation for both mother and fetus.